Thin film transistor liquid crystal displays (TFT LCDs) are a well known type of displays. One advanced type of TFTLCD is the fringe field switching TFT LCD, or FFS TFTLCD. Fringe field switching is considered to be a type of in-plane switching LCD; i.e., an LCD for which the electrodes performing the switching of pixels are in a single plane and formed on a single substrate on one side of the liquid crystals. (Other LCD technologies require that electrodes be placed in a “sandwich” configuration on two different substrates on both sides of the liquid crystals). An example of an FFS TFT LCD is described by Lee, Seung Hee et al., “Ultra-FFS TFT-LCD with Super Image Quality, Fast Response Time, and Strong Pressure-Resistant Characteristics,” Journal of the Society for Information displays Oct. 2, 2002. The above publication is hereby incorporated by reference herein in its entirety for all purposes.
Furthermore, FFS LCDs usually require the use of a common layer. The common layer can be a single electrode that is used for switching all pixels. Thus, the common layer can be referred to as a common electrode. Each pixel may also include a pixel electrode and the switching of a pixel may be performed by varying a voltage between individual pixel electrodes and the common electrode. In some embodiments different common electrodes may be used for different rows of pixels.
The common electrode can be the same for all pixels (or, alternatively, all pixels in a particular row) and need not be individually switched for individual pixels. Each pixel electrode can be individually switched by the use of a transistor connected to a data and gate line. A plurality of gate and data lines can be provided in a lattice covering the display so that each pixel is connected to a respective gate and data line. This may allow the switching of individual pixel electrodes. Switching of an electrode indicates loading and/or removing charge to/from the electrode in order to change the voltage of an electrode.
Because of the need to use higher resistance transparent conductors to form the common electrode, the switching rate of the common electrode and, subsequently, the refresh rate of the display can be limited. Furthermore, to minimize the amount of current that has to flow across these higher resistance paths, FFS TFT LCDs are usually limited in size.